Abstract

Imaging and spectroscopy of individual CdSenanocrystals have been performed with the scanning tunneling microscope (STM) on atomically resolved hydrogenated Si(100) surfaces. The CdSenanocrystals have been deposited under vacuum onto the surface by using the pulse valve method. Two different types of CdSenanocrystals, capped either with trioctylphosphine oxide ligands or with cadmium stearate ligands, have been studied to optimize their anchoring to the surface. The spectroscopy shows a characteristic resonant excitation spectrum through the unoccupied levels of the nanocrystals with no significant charging effect. This suggests that the nanocrystals are weakly coupled to the surface, thus requiring a stronger coupling with the STM tip to achieve a measurable tunnel current. These results demonstrate the importance of depositing nanocrystals on clean and atomically well-defined surfaces for reliable measurement of their properties.

Received 04 March 2005Accepted 18 June 2005Published online 29 July 2005

Acknowledgments:

We wish to thank the European Research Training Network “Atomic and Molecular Manipulations; a New Tool in Science and Technology” (AMMIST) and the European STREP “Nanoman” (Contract No. NMP4-CT-2003-550660) programs for financial support.